(spěr'ē) American neurobiologist who pioneered the behavioral investigation of "split-brain" animals and humans, establishing that each hemisphere of the brain controls specific higher functions. He shared with American neurophysiologist David H. Hubel and Swedish neurophysiologist Torsten N. Wiesel the 1981 Nobel Prize for physiology or medicine.

Our Living Language: Ever wondered what it's like to see the world upside-down and backwards? Some salamanders found out in the 1930s. They were experimental subjects in the lab of Roger Sperry, who had made his first big splash on the scientific community by showing that the functions of specific motor nerves in mammals were hardwired and unchangeable. Salamanders, unlike mammals, can regenerate nerves, so Sperry cut through their optic nerves and rotated their eyeballs 180 degrees. When the nerve grew back, it was somehow "guided back" to its original termination sites, resulting in the salamanders' visual field being radically altered. While this work was pathbreaking, Sperry's most famous experiments involved work with the brain in which the corpus callosum, the thick network of nerves that connects the left and right cerebral hemispheres, had been severed (resulting in a "split brain"). Sperry showed first that the hemispheres of split-brain cats learned tasks separately, and with equal facility, and were essentially independent cognitive organs. He then turned to humans, using patients whose corpora callosa had been severed as treatment for epilepsy (widely done at the time). Using these patients Sperry was able to demonstrate that the two hemispheres are functionally distinct: the left hemisphere is dominant in verbal and analytical tasks, while the right hemisphere is dominant in music and spatial tasks. The results of Sperry's and his colleagues' research led to the construction of a map of the brain and also to his sharing the Nobel Prize for physiology or medicine in 1981.